1. Field of Invention
The present disclosure relates to a prosthetic device system for repairing ball-and-socket type joints in a human body. More particularly the disclosure relates to a modular anatomic adjustable prosthetic device system for the shoulder and hip joints.
2. Description of Prior Art
A joint replacement procedure is sometimes necessary to repair a joint having a diseased or damaged articulating surface. Such a procedure involves removal of the diseased or damaged portions of the joint and replacing them with a prosthetic implant. This is often a desirable procedure for ball-and-socket type joints, particularly the shoulder and hip joints. A shoulder joint replacement procedure, for example, often involves removal of the humeral head and replacement thereof with an implant including a stem and a head. It is important that the implant be positioned correctly within the joint in order to ensure that appropriate joint kinematics, including range of motion, are preserved so as to replicate, as closely as possible, those of the original joint.
The classical prosthetic humeral component is known as the NEER-type and is a one-piece component which is available in many different sizes for replacement of the upper portion of the humerus. The classical humeral component has a stem which is designed to extend downwardly into a cavity formed within the humerus and which is secured with cement or with coatings which promote bone ingrowth to secure the stem. The stem is provided with a generally hemispherical head portion which is configured to replace the head of the organic humerus. However, the orientation of the humeral head relative to the stem varies from patient to patient. Therefore, it is desirable that the orientation of the humeral head be adjustable.
One adjustable device is described in U.S. Pat. No. 5,741,335 to Gerber et al. The shoulder prosthesis of Gerber et al. includes a humeral stem designed to be implanted within the patient's humeral canal and a head portion designed to cooperate with the glenoid cavity of a shoulder. The head portion has a spherical shape generated by revolution about an axis. A spherical socket is formed in the head portion for housing a ball that is fixed to a proximal end of the stem. The axis of revolution of the head portion is off-set with respect to the center of the ball. The assembly formed by the socket and the ball constitutes a joint capable of making the orientation of the head portion vary in relation to the stem by rotation about the center of the ball. The head portion is locked to the stem by a conical push rod which moves into an axial conical bore under the action of a tightening screw. The push rod causes compression of the ball against the spherical cavity by blocked lateral expansion of the ball thereby locking the head portion on the stem.
However, there is a need for prosthetic device system that allow quick and precise adjustment of the position of the humeral head during trial reduction, and once an optimal placement of the humeral head is determined, positively locks the prosthesis in that position.